The present invention relates to a supersonic flaw detecting system and, more particularly, to a supersonic flaw detecting system which is capable of successively conducting C-scope display and A-scope display and investigating any flaws in an object to be inspected from the both displays.
A supersonic flaw detecting system has been used for investigation of any internal flaw of an object such as a semiconductor, metal sheet and ceramics structure. The known supersonic flaw detecting system can be sorted into three types according to the type of display: namely, an A-scope display type, a B-scope display type and C-scope display type. The A-scope display type flaw detecting system has a probe which is energized to emit a supersonic wave towards an object, and an oscilloscope which displays waves reflected from the object, for example, with the axis of abscissa representing time and the axis of ordinate representing amplitudes of the waves, so as to permit surface echo reflected from the surface of the object, flaw echo reflected from the flaw and bottom echo reflected from the bottom surface of the object to be observed, so that the depth of the flaw from the object surface can be learned by measuring the time difference between the peaks of the surface echo and the flaw echo, and at the same time, the size of the flaw can be learned by reading the maximum or minimum amplitude of the flaw echo.
The B-scope display type flaw detecting system has a probe which scans the object only in one direction, and a monitor T.V. which displays the surface echo, flaw echo and bottom echo in terms of gradation according to the intensities of these echos, with the axis of abscissa representing the distance of movement of the probe and the axis of ordinate representing the depth (distance) in section of the object. The monitor T.V., therefore, can display the vertical section of the object including flaw information, so that the presence and the position of the flaw can be learned with a concept of area of a plan.
The C-scope display type flaw detecting system has a probe which scans the object both in vertical and horizontal directions, and a monitor T.V. which displays the flaw echo from a certain region of depth of the object determined by the gate width of a gate circuit, with the axis of abscissa and the axis of ordinate representing, respectively, the distances of the lateral (X direction) and longitudinal (Y direction) movements of the probe, in terms of gradation according to the intensity of the flaw echo. The monitor T.V., therefore, can display the cross-section of the object, including flaw information, so that the presence of the flow can be learned over the whole portion of the object.
A supersonic flaw detecting system has been also known which can conduct both the A-scope display and the C-scope display. In the use of this flaw detecting system, at first the presence, position and size of any flaw are roughly sounded by A-scope displays on a plurality of portions of the object and, thereafter, requirements for obtaining a clear C-scope display, such as gate width, amplifier gain of a pulse-receiver, focal position, i.e., the height of the probe (when the probe is of focus type) are determined in accordance with the A-scope information, and then the system is adjusted in accordance with the requirements and the C-scope display is conducted, thereby obtaining the detail of the flaw information over the entire portion of the object.
All the known flaw detecting system mentioned above, however, require laborious works with high degree of skill of an operator, as well as time, for obtaining exact flaw information over the entire portion of the object. Namely, the flaw detection by the A-scope type detecting system requires repetition of a considerably large number of A-scope displays for covering the entire area of the object, because each display provides only information of a portion just below the probe. In addition, since the previous information is extinguished from the oscilloscope, the operator has to compose the image of the flaws in the form of a line or a plane in his brain, which requires a high degree of skill and experience. The flaw detection by the B-scope type system also requires repetition of scanning and display operations as well as the brain work of an operator to provide flaw information in the form of a plane. The C-scope type detecting system permits the presence of any flaw to be investigated over the entire portion of the object, but cannot directly provide the exact information about the depth of the flaw. The exact depth information may be obtained by narrowing the gate width, but this causes a risk of exclusion of flaw echos from the depth other than the region corresponding to the narrowed gate width. Thus, in this case, the C-scope display has to be conducted on a plurality of depth regions in order to obtain flaw information over the full depth of the object. On the other hand, when the gate idth is widened, the disadvantage would occur that, when two or more flaws exist in an overlapping manner at different depths, the number of such flaws cannot be discriminated.
The flaw detecting system which conducts the A-scope display followed by the C-scope display also requires much time and labour because the initial A-scope display has to be conducted on a multiplicity of points until the presence of flaw is investigated over the entire portion of the object.